Please start a different topic for this, but the quick response here is that I can’t really say anything based on this description. If your two machines are in the same region, then the proxy does already round-robin traffic between machines, as long as both are healthy. However, if they are in different regions, then the proxy will always prioritize ones that are in a region closer to the client.
If you think that this is happening even with machines in the same region, having your app name and/or machine IDs would be helpful. But again, please start a new topic for this.